I dont have a 21" wheel but from what i understand is that you need to make the rear fender mounting holes larger so the rear of the fender can pick up alil and give you the clearance you need. Or at least loosen the fender bolts and make sure that is the problem before you drill them out

Theres supposed to be a little resistance there. Don't know what year but make sure your abs is hooked up properly within the tabs if you have it. Also like Rlaf75 said make sure your reem out your back holes on the fender, so you can tilt it up a bit.

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